Module for fast recognition of the pressed key. More...

#include <keyrecognizer.h>

Inheritance diagram for KeyRecognizer:

Collaboration diagram for KeyRecognizer:

Public Member Functions
	KeyRecognizer (KeyRecognizerCallback *callback)
	Constructor of the KeyRecognizer. More...

	~KeyRecognizer ()

void	init (bool optimize)
	Initialization of the KeyRecognizer. More...

void	recognizeKey (bool forceRestart, const Piano *piano, FFTDataPointer fftPointer, int selectedKey, bool keyForced)
	Start key recognition. More...

Public Member Functions inherited from SimpleThreadHandler
	SimpleThreadHandler ()
	Constructor. More...

virtual	~SimpleThreadHandler ()
	virtual destructor calls stop More...

virtual void	start ()
	Start the thread. More...

virtual void	stop ()
	Stop the thread. More...

Private Member Functions
void	workerFunction () overridefinal
	Main worker function for executing the key recognition thread. More...

double	detectForcedFrequency ()
	Detect forced key. More...

double	detectFrequencyInTreble ()
	Detect keys in the treble. More...

void	constructLogSpec ()
	Construct logarithmic spectrum. More...

void	signalPreprocessing ()
	Preprocessing of the signal. More...

void	defineKernel ()
	Define the kernel vector for key recognition. More...

double	estimateFrequency ()
	Estimate frequency for a given log-log spectrum. More...

int	findNearestKey (double f)
	Find the nearest key for a given frequency. More...

double	mtof (int m)
	Map bin index to frequency. More...

int	ftom (double f)
	Map frequency to bin index. More...

void	Write (std::string filename, std::vector< double > &v, bool log=true)

Private Attributes
KeyRecognizerCallback *	mCallback
	Pointer to the caller. More...

FFTDataPointer	mFFTPtr
	Pointer to Fourier transform. More...

double	mConcertPitch
	Actual frequency of the A-key. More...

const Piano *	mPiano
	Pointer to the piano data. More...

int	mNumberOfKeys
	Number of piano keys. More...

int	mKeyNumberOfA
	Index of the A-key. More...

FFT_Implementation	mFFT
	Instance of FFT implementation. More...

std::vector< double >	mLogSpec
	Logarithmic spectrum (LogSpec) More...

std::vector< double >	mFlatSpectrum
	DoubleLogarithmic spectrum (LogLogSpec) More...

FFTComplexVector	mKernelFFT
	Fourier transform of the kernel. More...

FFTComplexVector	mFlatFFT
	Fourier transform of LogLogSpec. More...

FFTRealVector	mConvolution
	Convolution vector. More...

int	mSelectedKey
	Number of the actually selected key. More...

bool	mKeyForced
	Flag indicating that the key is forced. More...

Static Private Attributes
static const int	M = 1024
	Number of bins (powers of 2,3,5) More...

static const double	fmin = 20
	Frequency of bin 0. More...

static const double	fmax = 10000
	Frequency of bin M-1. More...

static const double	logfmin = log(fmin)
	Log of minimal frequency. More...

static const double	logfmax = log(fmax)
	Log of maximal frequency. More...

Additional Inherited Members
Static Public Member Functions inherited from SimpleThreadHandler
static void	setThreadName (std::string s)
	Specify the name of the thread. More...

Protected Member Functions inherited from SimpleThreadHandler
virtual void	exceptionCaught (const EptException &e)
	EPT exception handling. More...

void	setCancelThread (bool b)
	Cancel-flag setter method, thread-safe. More...

bool	cancelThread () const
	Cancel-flag getter method, thread-safe. More...

void	msleep (double milliseconds)
	Sleep function for staying idle. More...

bool	isThreadRunning () const
	Flag to check if the thread is running. More...

Detailed Description

Module for fast recognition of the pressed key.

When a key is pressed, the SignalAnalyzer calls the function recognizeKey to start an independent thread for key recognition on the basis of the current Fourier transform. The key recognizer transmits the estimated frequency and the corresponding key number via a callback function.

Definition at line 57 of file keyrecognizer.h.

Constructor & Destructor Documentation

KeyRecognizer::KeyRecognizer ( KeyRecognizerCallback * callback )

Constructor of the KeyRecognizer.

Parameters

callback : Pointer to the instance of the callback.

Definition at line 52 of file keyrecognizer.cpp.

KeyRecognizer::~KeyRecognizer ( )

inline

Definition at line 66 of file keyrecognizer.h.

Member Function Documentation

void KeyRecognizer::constructLogSpec ( )

private

Construct logarithmic spectrum.

This function maps the FFT spectrum, which is linear in the frequency, to a logarithmically binned spectrum. To this end the amplitudes of the FFT power spectrum are evently distributed into bins of the logarithmic spectrum (mLogSpec).

Definition at line 304 of file keyrecognizer.cpp.

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void KeyRecognizer::defineKernel ( )

private

Define the kernel vector for key recognition.

The tuner needs to recognize the key that is pressed. The essential part in the recognition procedure is a kernel function which is convolved linearly with the actually measured spectrum. It has positive peaks in those positions where partials are expected and negative peaks in the place of wrong partials. It is stored in a in a STL map.

Definition at line 388 of file keyrecognizer.cpp.

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double KeyRecognizer::detectForcedFrequency ( )

private

Detect forced key.

If a key is forced we search for the maximum of the FFT in the vicinity of the forced key with a width of a bit less than a half tone.

Returns: Frequency in Hz

Definition at line 188 of file keyrecognizer.cpp.

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double KeyRecognizer::detectFrequencyInTreble ( )

private

Detect keys in the treble.

For very high notes the kernel method is not suitable. This function detects whether one of the very high keys has been hit. This is done by comparing the second and the first moment of the FFT. If the ratio is above the threshold, indicating a high key, the frequency is determined simply by searching for the maximal peak in the range from 1..5 kHz.

Returns: Frequency in Hz

Definition at line 224 of file keyrecognizer.cpp.

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double KeyRecognizer::estimateFrequency ( )

private

Estimate frequency for a given log-log spectrum.

This function estimates the frequency of a pressed piano key. To this end the logarithmically binned log spectrum is convolved with the recognition kernel for all frequencies. For speedup this convolution product is carried out by two Fourier transformations (in log space instead of real space) with an ordinary multiplication in between. The m-value (slot) where the response of the kernel is maximal is then used as a first estimate of the frequency.

Returns: Estimated frequency in Hz

Definition at line 443 of file keyrecognizer.cpp.

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int KeyRecognizer::findNearestKey ( double f )

private

Find the nearest key for a given frequency.

This function determines the most likely index of a key for a given frequency, referring to the actual concert pitch.

Parameters

f	: Frequency in Hz

Returns: Index of the key in the range 0..mNumberOfKeys

Definition at line 468 of file keyrecognizer.cpp.

int KeyRecognizer::ftom ( double f )

private

Map frequency to bin index.

Convert frequency to logspec index.

The key recognizer performs a logarithmic binning independent of the one carried out in the FFTAnalyzer. To this end the frequency f is mapped to an integer index m. The formula reads:

\[ m(f) = \left[M \frac{\ln(f-f_{min})}{\ln(f_{max}-f_{min})}\right], \]

where M is the total number of bins. The expression is rounded to an integer.

Parameters

f	: Frequency in Hz

Returns: Integer index

Definition at line 271 of file keyrecognizer.cpp.

void KeyRecognizer::init ( bool optimize )

Initialization of the KeyRecognizer.

This function defines the kernel and optimizes the plan for the FFT. Optimization will take a while to be finished.

Parameters

optimize : true if the FFT should be optimized

Definition at line 82 of file keyrecognizer.cpp.

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double KeyRecognizer::mtof ( int m )

private

Map bin index to frequency.

Convert logspec index to frequency.

This function maps the logarithmic binning index back to the frequency. It is the inverse function of ftom:

\[ f(m) = f_{min} + (f_{max}-f_{min})^{m/M} \,. \]

Parameters

m	: the index

Returns: frequency in Hz

Definition at line 286 of file keyrecognizer.cpp.

void KeyRecognizer::recognizeKey	(	bool	forceRestart,
		const Piano *	piano,
		FFTDataPointer	fftPointer,
		int	selectedKey,
		bool	keyForced
	)

Start key recognition.

Function to start the key recognition thread. This function is called by the SignalAnalyzer.

Parameters

forceRestart	: true if restart of the thread is forced
piano	: pointer to the piano data
fftPointer	: pointer to the actual FFT
selectedKey	: Number of the selected key (-1 if none)
keyForced	: Boolean flag saying whether the selected key is forced

Definition at line 111 of file keyrecognizer.cpp.

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void KeyRecognizer::signalPreprocessing ( )

private

Preprocessing of the signal.

The purpose of this function is to convert the logarithmically binned spectrum (called logspec), which is logarithmic in the frequency, also logarithmically in the amplitude. The result is a double-logarithmic spectrum, i.e., logarithmic in its binning and also in its value. Values <= 0 are mapped to zero.

Some spectra, in particular those of the high keys, show a broad noise background which varies only smoothly with the frequency. The second part of the function substracts a gliding average over a certain window, centereing the loglog spectrum around the zero line.

Definition at line 332 of file keyrecognizer.cpp.

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void KeyRecognizer::workerFunction ( )

finaloverrideprivatevirtual

Main worker function for executing the key recognition thread.

Implements SimpleThreadHandler.

Definition at line 146 of file keyrecognizer.cpp.

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void KeyRecognizer::Write	(	std::string	filename,
		std::vector< double > &	v,
		bool	log = `true`
	)

private

Definition at line 485 of file keyrecognizer.cpp.

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Member Data Documentation

const double KeyRecognizer::fmax = 10000

staticprivate

Frequency of bin M-1.

Definition at line 62 of file keyrecognizer.h.

const double KeyRecognizer::fmin = 20

staticprivate

Frequency of bin 0.

Definition at line 61 of file keyrecognizer.h.

const double KeyRecognizer::logfmax = log(fmax)

staticprivate

Log of maximal frequency.

Definition at line 103 of file keyrecognizer.h.

const double KeyRecognizer::logfmin = log(fmin)

staticprivate

Log of minimal frequency.

Definition at line 102 of file keyrecognizer.h.

const int KeyRecognizer::M = 1024

staticprivate

Number of bins (powers of 2,3,5)

Definition at line 60 of file keyrecognizer.h.

KeyRecognizerCallback* KeyRecognizer::mCallback

private

Pointer to the caller.

Definition at line 86 of file keyrecognizer.h.

double KeyRecognizer::mConcertPitch

private

Actual frequency of the A-key.

Definition at line 88 of file keyrecognizer.h.

FFTRealVector KeyRecognizer::mConvolution

private

Convolution vector.

Definition at line 97 of file keyrecognizer.h.

FFT_Implementation KeyRecognizer::mFFT

private

Instance of FFT implementation.

Definition at line 92 of file keyrecognizer.h.

FFTDataPointer KeyRecognizer::mFFTPtr

private

Pointer to Fourier transform.

Definition at line 87 of file keyrecognizer.h.

FFTComplexVector KeyRecognizer::mFlatFFT

private

Fourier transform of LogLogSpec.

Definition at line 96 of file keyrecognizer.h.

std::vector<double> KeyRecognizer::mFlatSpectrum

private

DoubleLogarithmic spectrum (LogLogSpec)

Definition at line 94 of file keyrecognizer.h.

FFTComplexVector KeyRecognizer::mKernelFFT

private

Fourier transform of the kernel.

Definition at line 95 of file keyrecognizer.h.

bool KeyRecognizer::mKeyForced

private

Flag indicating that the key is forced.

Definition at line 99 of file keyrecognizer.h.

int KeyRecognizer::mKeyNumberOfA

private

Index of the A-key.

Definition at line 91 of file keyrecognizer.h.

std::vector<double> KeyRecognizer::mLogSpec

private

Logarithmic spectrum (LogSpec)

Definition at line 93 of file keyrecognizer.h.

int KeyRecognizer::mNumberOfKeys

private

Number of piano keys.

Definition at line 90 of file keyrecognizer.h.

const Piano* KeyRecognizer::mPiano

private

Pointer to the piano data.

Definition at line 89 of file keyrecognizer.h.

int KeyRecognizer::mSelectedKey

private

Number of the actually selected key.

Definition at line 98 of file keyrecognizer.h.

The documentation for this class was generated from the following files:

/home/hinrichsen/Dokumente/Aktuell/EPT/Entropy-Piano-Tuner/core/analyzers/keyrecognizer.h
/home/hinrichsen/Dokumente/Aktuell/EPT/Entropy-Piano-Tuner/core/analyzers/keyrecognizer.cpp

Public Member Functions

Private Member Functions

Private Attributes

Static Private Attributes

Additional Inherited Members

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation